Sister Character Designs

Since showing my film idea at uni, I had the story that two sisters would come across a swamp creature and the creature would take the youngest sister to her home under the water to show her her beautiful home but accidentally start drowning the sister. For a while I was greatly concentrating on the sister's relationship and what their story was: Do they get on? why not? how old are they? what are their interests? etc

Older sister: I wanted the older sister to be at least 16/17 years old and be having the pressures of society upon her, such as having to look pretty etc. I wanted to give a a very curvy body, almost pear spaced with s big bum which she's a bit self conscious of. She doesn't completely have patience for her younger sister's fooling around.

Younger sister: The younger sister I aimed to be about 9/10 years old, she is meant to be playful and a tomboy, having no worries of being an adult. She is very interactive with her surroundings such as playing with sticks, climbing trees etc. and is always curious to explore new things and animals.

I was finding it hard to somehow present the sister's relationship and for the meeting the creature and resolve a message to the story in 3 minutes or under. I then cut it down to just the one sister, the youngest one. I only think this would have worked to have two sisters if this was more of a 10 min short, which of course I don't have the time for.